1.Field of the Invention:
The present invention relates generally to continuous casting equipment and more particularly to a cast piece guide roll segment in continuous casting equipment.
2. Description of the Prior Art:
Curved-type continuous casting equipment includes a mold having a curved inner wall, a secondary cooling zone having a curved guide path including therein a plurality of rolls arranged along any suitable curved portion, such as an arc, parabola, hyperbola or the like, for guiding the cast piece leaving the mold from the vertical position to the horizontal position, pinch rolls disposed subsequently to the secondary cooling zone for continuously drawing the cast piece, and a cutter for cutting the cast piece drawn by the pinch rolls into any desired size. For the roll groups of the secondary cooling zone, in such curved-type continuous casting equipment, it is necessary to replace the rolls due to wear of the rolls in this zone caused by constant contact thereof with the cast piece, due to damage of the rolls caused by a thermal effect from the cast piece, or due to the requirement for changing the cast piece size. In view of the feasibility of roll replacement, it is practiced that the roll groups in the secondary cooling zone are separated into cast piece guide roll segments having a plurality of roll pairs as a unit. Since each of the rolls in the cast piece guide roll segment is subjected to hydrostatic pressure due to unsolidified molten steel remaining in the interior of the cast piece, thereby producing the bulging of the solidified shell of the cast piece, sufficient mechanical strength to prevent such bulging is required. Particularly, with the recent tendency to enlarge the cast piece size, the construction itself of the cast piece guide roll segment is correspondingly enlarged and increased in weight, resulting in difficulty in the replacement operation of the cast piece guide roll segment. Particularly, the cast piece guide roll segment in the portion comprising the curved guide path is disposed in a curved and inclined condition, and therefore, it must be removed in the radial direction of the curved path or in the direction transverse to the guide path, thereby rendering the replacement of the cast piece guide roll segment extremely difficult. It is therefore very difficult to accomplish a smooth replacing operation of the cast piece guide roll segment. As a result, the cast piece guide roll segment requires a long time for replacement, and the shut-down time of the equipment is necessarily increased, that is, the high productivity inherent in such equipment is hindered.
In such continuous casting equipment, it is also known that a failure in the form of a rupture occurs when the solidified shell of the cast piece leaving the mold is broken and unsolidified molten steel in the interior flows out. The generation of this rupture causes interruption of the operation of the equipment, such that the cast piece is allowed to remain in the cast piece guide roll segment of the secondary cooling zone. As the cast piece remaining in the cast piece guide roll segment cools, it contracts and curves inwardly to a greater extent that the curved cast steel guide path as the cooling progresses. Therefore, the cast piece itself acts as a large spring. This contraction and curving of the cast piece exerts an undue force of deformation on the rolls of the secondary cooling zone supporting the cast piece, that is, on each roll of the cast piece guide roll segment, and the cast piece guide roll segment breaks under the force of deformation. Particularly, such tendency is extensive in the curved-type continuous casting equipment wherein the secondary cooling zone is in the form of any of the continuous curves as described above. Therefore, it has been considered necessary to protect the cast piece guide roll segment during generation of the rupture as an inherent problem in such continuous casting equipment.